Accounting for the Greenhouse Gas Emission Intensity of Regional Electricity Transfers

Accurately quantifying greenhouse gas (GHG) emissions is essential for climate policy implementation but challenging in the case of electricity transfers across regulatory jurisdictions. Regulating emissions associated with delivered electricity is further complicated by contractual arrangements for dynamic electricity transfers that confound emission accounting approaches rooted in the physics of grid operations. Here, we propose a novel consumption-based accounting methodology to reconcile the nominal and the physical flows of electricity from generators to consumers. We also compare capacity factor-based and regression-based approaches for estimating default emission factors, in the absence of fully specified nominal electricity flows. As a case study, we apply this approach to assess the methods by which California regulators quantify specified and unspecified electricity imports and their associated GHG emissions. Collectively, these efforts illustrate principles for a comprehensive, empirical accounting framework that could inform efforts to improve the accuracy and consistency of policies regulating regional electricity transfers.